package Netty之NIO背景.selector;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.Iterator;

/**
 * @author ChenweiLin
 * @create 2021-12-07 15:29
 */
public class WriteServer {
    public static void main(String[] args) throws IOException {
        ServerSocketChannel ssc = ServerSocketChannel.open();
        ssc.configureBlocking(false);

        Selector selector = Selector.open();

        ssc.register(selector, SelectionKey.OP_ACCEPT);
        ssc.bind(new InetSocketAddress(8080));

        while(true){
            selector.select();
            Iterator<SelectionKey> iter = selector.selectedKeys().iterator();
            while (iter.hasNext()){
                SelectionKey key = iter.next();
                iter.remove();
                if(key.isAcceptable()){
                    SocketChannel sc = ssc.accept();
                    sc.configureBlocking(false);
                    SelectionKey sckey = sc.register(selector, 0, null);
                    //1.向客户端发送大量数据
                    StringBuilder sb = new StringBuilder();
                    for (int i = 0; i < 5000000; i++) {
                        sb.append("a");
                    }
                    ByteBuffer buffer = Charset.defaultCharset().encode(sb.toString());
                    //2.返回值代表实际写入的字节数
                    int write = sc.write(buffer);
                    System.out.println(write);

                    //3.判断是否有剩余内容
                    if (buffer.hasRemaining()){
                        //4.关注可写事件
                        //拿到原来的关注事件，并添加可写事件
                        sckey.interestOps(sckey.interestOps() + SelectionKey.OP_WRITE);
                        //5.把未写完的数据挂到sckey上 以附件的形式
                        sckey.attach(buffer);
                    }
                } else if(key.isWritable()){
                    //拿到附件
                    ByteBuffer buffer = (ByteBuffer)key.attachment();
                    SocketChannel sc = (SocketChannel)key.channel();
                    int write = sc.write(buffer);
                    System.out.println(write);
                    //6.清理操作
                    if(!buffer.hasRemaining()){//如果buffer没有剩余了，即buffer已经被channel写完了
                        key.attach(null);//附件清空，需要清除buffer
                        key.interestOps(key.interestOps() - SelectionKey.OP_WRITE);//不需要再关注可写事件

                    }
                }
            }
        }
    }
}
